Ultra-dense wavelength division multiplexing/demultiplexing devices

ABSTRACT

A family of ultra-dense wavelength division multiplexing/demultiplexing devices are disclosed. In the case of an ultra-dense wavelength division multiplexing device, a wavelength division multiplexing device is used for combining at least one plurality of monochromatic optical beams into a corresponding at least one single, multiplexed, polychromatic optical beam, wherein the wavelength division multiplexing device has an input element and an output element. A plurality of optical input devices is disposed proximate the input element, wherein each of the plurality of optical input devices communicates a plurality of monochromatic optical beams to the wavelength division multiplexing device for combining the plurality of monochromatic optical beams into a single, multiplexed, polychromatic optical beam. A corresponding plurality of optical output devices is disposed proximate the output element, wherein each of the plurality of optical output devices receives a corresponding single, multiplexed, polychromatic optical beam.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of Ser. No. 09/583,764 filedMay 31, 2000 now U.S. Pat. No. 6,343,169 which is a continuation-in-partapplication of U.S. patent application Ser. No. 09/257,045 ClientReference No. D-97031-CNT), filed Feb. 25, 1999 now U.S. Pat. No.6,137,933; U.S. patent application Ser. No. 09/323,094 Client ReferenceNo. D-99001), filed Jun. 1, 1999 now U.S. Pat. No. 6,263,135; U.S.patent application Ser. No. 09/342,142 Client Reference No. D-99002),filed Jun. 29, 1999 now U.S. Pat. No. 6,289,155; U.S. patent applicationSer. No. 09/382,492 Client Reference No. D-99004), filed Aug. 25, 1999now U.S. Pat. No. 6,404,945; U.S. patent application Ser. No. 09/382,624Client Reference No. D-99005), filed Aug. 25, 1999 now U.S. Pat. No.6,271,970; U.S. patent application Ser. No. 09/363,041 Client ReferenceNo. D-99014), filed Jul. 29, 1999 now U.S. Pat. No. 6,243,513; U.S.patent application Ser. No. 09/363,042 Client Reference No. D-99015),filed Jul. 29, 1999 now U.S. Pat. No. 6,236,780; U.S. patent applicationSer. No. 09/392,670 Client Reference No. D-99016), filed Sep. 8, 1999now U.S. Pat. No. 6,298,182; and U.S. patent application Ser. No.09/392,831 Client Reference No. D-99017), filed Sep. 8, 1999 now U.S.Pat. No. 6,181,853; all of which are hereby incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates generally to wavelength divisionmultiplexing and demultiplexing and, more particularly, to ultra-densewavelength division multiplexing/demultiplexing devices.

BACKGROUND OF THE INVENTION

Wavelength division multiplexing (WDM) is a rapidly emerging technologythat enables a very significant increase in the aggregate volume of datathat can be transmitted over optical fibers. Prior to the use of WDM,most optical fibers were used to unidirectionally carry only a singledata channel at one wavelength. The basic concept of WDM is to launchand retrieve multiple data channels in and out, respectively, of anoptical fiber. Each data channel is transmitted at a unique wavelength,and the wavelengths are appropriately selected such that the channels donot interfere with each other, and the optical transmission losses ofthe fiber are low. Today, commercial WDM systems exist that allow forthe transmission of 2 to 100 simultaneous data channels.

WDM is a cost-effective method of increasing the volume of data(commonly termed bandwidth) transferred over optical fibers. Alternatecompeting technologies for increasing bandwidth include the burying ofadditional fiber optic cable or increasing the optical transmission rateover optical fiber. The burying of additional fiber optic cable is quitecostly as it is presently on the order of $15,000 to $40,000 perkilometer. Increasing the optical transmission rate is limited by thespeed and economy of the electronics surrounding the fiber optic system.One of the primary strategies for electronically increasing bandwidthhas been to use time division multiplexing (TDM), which groups ormultiplexes multiple lower rate electronic data channels together into asingle very high rate channel. This technology has for the past 20 yearsbeen very effective for increasing bandwidth. However, it is nowincreasingly difficult to improve transmission speeds, both from atechnological and an economical standpoint. WDM offers the potential ofboth an economical and technological solution to increasing bandwidth byusing many parallel channels. Further, WDM is complimentary to TDM. Thatis, WDM can allow many simultaneous high transmission rate TDM channelsto be passed over a single optical fiber.

The use of WDM to increase bandwidth requires two basic devices that areconceptually symmetrical. The first device is a wavelength divisionmultiplexer. This device takes multiple beams, each with discretewavelengths that are initially spatially separated in space, andprovides a means for spatially combining all of the different wavelengthbeams into a single polychromatic beam suitable for launching into anoptical fiber. The multiplexer may be a completely passive opticaldevice or may include electronics that control or monitor theperformance of the multiplexer. The input to the multiplexer istypically accomplished with optical fibers, although laser diodes orother optical sources may also be employed. As mentioned above, theoutput from the multiplexer is a single polychromatic beam which istypically directed into an optical fiber.

The second device for WDM is a wavelength division demultiplexer. Thisdevice is functionally the opposite of the wavelength divisionmultiplexer. That is, the wavelength division demultiplexer receives apolychromatic beam from an optical fiber and provides a means ofspatially separating the different wavelengths of the polychromaticbeam. The output from the demultiplexer is a plurality of monochromaticbeams which are typically directed into a corresponding plurality ofoptical fibers or photodetectors.

To date, most WDM devices have been directed toward multiplexing ordemultiplexing a standard number of data channels. For example, many WDMdevices are specifically manufactured to multiplex 33 individual datachannels being carried on 33 corresponding monochromatic beams into asingle polychromatic beam carrying all 33 data channels, or todemultiplex a single polychromatic beam carrying 33 separate datachannels into 33 individual monochromatic beams each carrying acorresponding data channel. These WDM devices are typically limited to33 data channels due to the manner in which they have been manufacturedand the technologies employed to perform the multiplexing anddemultiplexing functions therein. For example, WDM devices employingfiber Bragg gratings and/or array waveguide gratings to performmultiplexing and demultiplexing functions are typically limited to thenumber of data channels that the WDM devices were specificallymanufactured to handle. Thus, if additional numbers of data channelsneed to be multiplexed and/or demultiplexed, additional WDM devices arerequired, at a corresponding additional cost. Alternatively, enhancedWDM devices employing these technologies may be designed to accommodateadditional numbers of data channels, but with corresponding additionaldesign, manufacturing, and testing costs. Also, such enhanced WDMdevices are typically larger in size so as to accommodate the increasednumber of data channels, thereby requiring more space to operate, whichusually translates into additional packaging costs.

In view of the foregoing, it would be desirable to provide a WDM devicewhich overcomes the above-described inadequacies and shortcomings. Moreparticularly, it would be desirable to provide an ultra-dense WDM devicewhich can accommodate additional data channels without requiringadditional WDM devices or significant design modifications.

OBJECTS OF THE INVENTION

The primary object of the present invention is to provide ultra-densewavelength division multiplexing/demultiplexing devices.

The above-stated primary object, as well as other objects, features, andadvantages, of the present invention will become readily apparent fromthe following summary and detailed descriptions, which are to be read inconjunction with the appended drawings.

SUMMARY OF THE INVENTION

According to the present invention, ultra-dense wavelength divisionmultiplexing/demultiplexing devices are provided. In the case of anultra-dense wavelength division multiplexing device, a wavelengthdivision multiplexing device is used for combining at least oneplurality of monochromatic optical beams into a corresponding at leastone single, multiplexed, polychromatic optical beam, wherein thewavelength division multiplexing device has an input element and anoutput element. A plurality of optical input devices is disposedproximate the input element, wherein each of the plurality of opticalinput devices communicates a plurality of monochromatic optical beams tothe wavelength division multiplexing device for combining the pluralityof monochromatic optical beams into a single, multiplexed, polychromaticoptical beam. A corresponding plurality of optical output devices isdisposed proximate the output element, wherein each of the plurality ofoptical output devices receives a corresponding single, multiplexed,polychromatic optical beam.

In accordance with other aspects of the present invention, thewavelength division multiplexing device comprises a diffraction gratingfor combining the at least one plurality of monochromatic optical beamsinto the corresponding at least one single, multiplexed, polychromaticoptical beam. The diffraction grating is preferably a reflectivediffraction grating oriented at the Littrow diffraction angle.Alternatively, the diffraction grating can be a transmissive diffractiongrating.

In accordance with further aspects of the present invention, the inputelement can beneficially be one of several items such as, for example, acollimating lens or a boot lens. Similarly, the output element canbeneficially be one of several items such as, for example, a focusinglens or a boot lens.

In accordance with still further aspects of the present invention, theplurality of optical input devices is beneficially a plurality of inputfiber coupling devices, wherein each of the plurality of input fibercoupling devices is arranged into an array of optical fibers, and eachof the optical fibers transmits a monochromatic optical beam to thewavelength division multiplexing device. Also, the plurality of opticalinput devices is beneficially a plurality of laser diode couplingdevices, wherein each of the plurality of laser diode coupling devicesis arranged into an array of laser diodes, and each of the laser diodestransmits a monochromatic optical beam to the wavelength divisionmultiplexing device. Further, the plurality of optical output devices isbeneficially a plurality of output fiber coupling devices, wherein eachof the plurality of output fiber coupling devices maintains at least oneoptical fiber, and each optical fiber receives a single, multiplexed,polychromatic optical beam from the wavelength division multiplexingdevice.

In the case of an ultra-dense wavelength division demultiplexing device,a wavelength division demultiplexing device is used for separating atleast one multiplexed, polychromatic optical beam into a correspondingat least one plurality of monochromatic optical beams, wherein thewavelength division demultiplexing device has an input element and anoutput element. A plurality of optical input devices is disposedproximate the input element, wherein each of the plurality of opticalinput devices communicates a single, multiplexed, polychromatic opticalbeam to the wavelength division demultiplexing device for separating thesingle, multiplexed, polychromatic optical beam into a plurality ofmonochromatic optical beams. A corresponding plurality of optical outputdevices is disposed proximate the output element, wherein each of theplurality of optical output devices receives a corresponding pluralityof monochromatic optical beams.

In accordance with other aspects of the present invention, thewavelength division demultiplexing device comprises a diffractiongrating for separating the at least one multiplexed, polychromaticoptical beam into the corresponding at least one plurality ofmonochromatic optical beams. The diffraction grating is preferably areflective diffraction grating oriented at the Littrow diffractionangle. Alternatively, the diffraction grating can be a transmissivediffraction grating.

In accordance with further aspects of the present invention, the inputelement can beneficially be one of several items such as, for example, acollimating lens or a boot lens. Similarly, the output element canbeneficially be one of several items such as, for example, a focusinglens or a boot lens.

In accordance with still further aspects of the present invention, theplurality of optical input devices is beneficially a plurality of inputfiber coupling devices, wherein each of the plurality of input fibercoupling devices maintains at least one optical fiber, and each opticalfiber transmits a single, multiplexed, polychromatic optical beam to thewavelength division demultiplexing device. Also, the plurality ofoptical output devices is beneficially a plurality of output fibercoupling devices, wherein each of the plurality of output fiber couplingdevices is arranged into an array of optical fibers, and each of theoptical fibers receives a monochromatic optical beam from the wavelengthdivision demultiplexing device. Further, the plurality of optical outputdevices is beneficially a plurality of photodetector coupling devices,wherein each of the plurality of photodetector coupling devices isarranged into an array of photodetectors, and each of the photodetectorsreceives a monochromatic optical beam from the wavelength divisiondemultiplexing device.

In accordance with still further aspects of the present invention, theat least one multiplexed, polychromatic optical beam can be at least twomultiplexed, polychromatic optical beams. If such is the case, theultra-dense wavelength division demultiplexing device may furthercomprise a splitter for splitting a single, pre-split, multiplexed,polychromatic optical beam into the at least two multiplexed,polychromatic optical beams. The single, pre-split, multiplexed,polychromatic optical beam can be split equally or unequally. Also, thesingle, pre-split, multiplexed, polychromatic optical beam can be splitin several manners such as, for example, according to beam wavelengthsor according to beam intensity.

The present invention also encompasses a method for increasing channelthroughput in a wavelength division demultiplexing device. The methodcomprises splitting a single, multiplexed, polychromatic optical beaminto at least two multiplexed, polychromatic optical beams, and thensimultaneously separating each of the at least two multiplexed,polychromatic optical beams into a corresponding at least twopluralities of monochromatic optical beams. The method also preferablycomprises collimating each of the at least two multiplexed,polychromatic optical beams, and focusing the corresponding at least twopluralities of monochromatic optical beams.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to facilitate a fuller understanding of the present invention,reference is now made to the appended drawings. These drawings shouldnot be construed as limiting the present invention, but are intended tobe exemplary only.

FIG. 1a is a side view of an ultra-dense wavelength divisionmultiplexing devise having a plurality of optical input devices and aplurality of optical output devices in accordance with the presentinvention.

FIG. 1b is a top view of the ultra-dense wavelength divisionmultiplexing device shown in FIG. 1a.

FIG. 1c is an end view of a portion of the ultra-dense wavelengthdivision multiplexing device shown in FIG. 1a.

FIG. 2a is a perspective view of a coupling device containing aplurality of laser diodes for replacing the plurality of optical inputfibers in the multiplexing device shown in FIG. 1a.

FIG. 2b is a perspective view of a coupling device containing aplurality of photodetectors for replacing the plurality of optical inputfibers in the demultiplexing device shown in FIG. 3a.

FIG. 3a is a side view of an ultra-dense wavelength divisiondemultiplexing device having a plurality of optical input devices and aplurality of optical output devices in accordance with the presentinvention.

FIG. 3b is a top view of the ultra-dense wavelength divisiondemultiplexing device shown in FIG. 3a.

FIG. 4 is a top view of a demultiplexing system employing an ultra-densewavelength division demultiplexing device having a plurality of opticalinput devices and a plurality of optical output devices in accordancewith the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1a and 1 b, there are shown a side view and a topview, respectively, of a preferred embodiment of an ultra-densewavelength division multiplexing/demultiplexing device 10 in accordancewith the present invention. The multiplexing device 10 comprises aplurality of optical input fibers 12, a plurality of input fibercoupling devices 14, a collimating/focusing lens 16, a reflectivediffraction grating 18, a plurality of output fiber coupling devices 20,and a plurality of optical output fibers 22. All of the above-identifiedcomponents of the multiplexing device 10 are disposed along an opticalaxis Z-Z of the multiplexing device 10, as will be described in moredetail below.

At this point it should be noted that the optical input fibers 12 andthe optical output fibers 22, as well as any other optical fibersdescribed herein as being used in conjunction with WDM devices inaccordance with the present invention, are single mode optical fibers.Of course, however, this does not limit the present invention WDMdevices to use with only single mode optical fibers. For example, thepresent invention WDM devices can also be used with multimode opticalfibers.

The plurality of optical input fibers 12 are grouped into threeone-dimensional input fiber arrays (i.e., three 1×33 arrays) by theplurality of input fiber coupling devices 14, while each of theplurality of optical output fibers 22 is secured to a corresponding oneof the plurality of output fiber coupling devices 20. Both the inputfiber coupling devices 14 and the output fiber coupling devices 20 areused for purposes of ease of optical fiber handling and precisionplacement, and can be formed of, for example, silicon V-grooveassemblies. Referring to FIG. 1c, there is shown an end view of theplurality of input fiber coupling devices 14 and the plurality of outputfiber coupling devices 20, along section A-A of FIGS. 1a and 1 b. Eachof the plurality of input fiber coupling devices 14 is arranged as a1×33 array for precisely and securely positioning thirty-three of theplurality of optical input fibers 12, while each of the plurality ofoutput fiber coupling devices 20 precisely and securely positions acorresponding one of the plurality of optical output fibers 22.

Returning to FIGS. 1a and 1 b, each of the plurality of optical inputfibers 12 transmits a single, monochromatic optical input beam 24, whileeach of the plurality of optical output fibers 22 receives a single,multiplexed, polychromatic optical output beam 26. Each of themonochromatic optical input beams 24 being transmitted from theplurality of optical input fibers 12 is carrying a single channel ofdata at a unique wavelength, which is preferably, but not required tobe, within the infrared (IR) region of the electromagnetic spectrum. Thesingle channel of data that is being carried by each monochromaticoptical input beam 24 is superimposed on each corresponding uniquewavelength by means (e.g., laser diodes connected to the plurality ofoptical input fibers 12), which are not shown here and which do not forma part of this invention, but are well known in the art. The uniquewavelengths of the monochromatic optical input beams 24 areappropriately preselected such that the data channels do not interferewith each other (i.e., there is sufficient channel spacing), and theoptical transmission losses through both the optical input fibers 12 andthe optical output fibers 22 are low, as is also well known in the art.

Each of the multiplexed, polychromatic optical output beams 26 beingreceived by the plurality of optical output fibers 22 is carrying aplurality of channels of data at the unique wavelengths of correspondingones of the plurality of monochromatic optical input beams 24. That is,a first of the multiplexed, polychromatic optical output beams 26 a iscarrying a plurality of channels of data (e.g., 33 channels of data) atthe unique wavelengths of the monochromatic optical input beams 24 athat are transmitted from the optical input fibers 12 a being preciselyand securely positioned by a first of the plurality of input fibercoupling devices 14 a. Similarly, a second of the multiplexed,polychromatic optical output beams 26 b is carrying a plurality ofchannels of data (e.g., 33 channels of data) at the unique wavelengthsof the monochromatic optical input beams 24 b that are transmitted fromthe optical input fibers 12 b being precisely and securely positioned bya second of the plurality of input fiber coupling devices 14 b.Similarly still, a third of the multiplexed, polychromatic opticaloutput beams 26 c is carrying a plurality of channels of data (e.g., 33channels of data) at the unique wavelengths of the monochromatic opticalinput beams 24 c that are transmitted from the optical input fibers 12 cbeing precisely and securely positioned by a third of the plurality ofinput fiber coupling devices 14 c.

The plurality of monochromatic optical input beams 24 a are combinedinto the multiplexed, polychromatic optical output beam 26 a through thecombined operation of the collimating/focusing lens 16 and thereflective diffraction grating 18, as will be described in more detailbelow. Similarly, the plurality of monochromatic optical input beams 24b are combined into the multiplexed, polychromatic optical output beam26 b through the combined operation of the collimating/focusing lens 16and the reflective diffraction grating 18, as will be described in moredetail below. Similarly still, the plurality of monochromatic opticalinput beams 24 c are combined into the multiplexed, polychromaticoptical output beam 26 c through the combined operation of thecollimating/focusing lens 16 and the reflective diffraction grating 18,as will be described in more detail below.

At this point it should be noted that the input fiber coupling device 14a and the output fiber coupling device 20 a are disposed offset from,but symmetrically about, the optical axis Z-Z of the multiplexing device10 so as to insure that the multiplexed, polychromatic optical outputbeam 26 a is directed to the optical output fiber 22 a secured to theoutput fiber coupling device 20 a, and not to any of the other opticaloutput fibers 22, or anywhere else. This offset spacing of the inputfiber coupling device 14 a and the output fiber coupling device 20 a isdetermined based upon the focusing power of the collimating/focusinglens 16, as well as the characteristics of the diffraction grating 18and the wavelengths of each of the monochromatic optical input beams 24a.

Similarly, the input fiber coupling device 14 b and the output fibercoupling device 20 b are disposed offset from, but symmetrically about,the optical axis Z-Z of the multiplexing device 10 so as to insure thatthe multiplexed, polychromatic optical output beam 26 b is directed tothe optical output fiber 22 b secured to the output fiber couplingdevice 20 b, and not to any of the other optical output fibers 22, oranywhere else. This offset spacing of the input fiber coupling device 14b and the output fiber coupling device 20 b is determined based upon thefocusing power of the collimating/focusing lens 16, as well as thecharacteristics of the diffraction grating 18 and the wavelengths ofeach of the monochromatic optical input beams 24 b.

Similarly still, the input fiber coupling device 14 c and the outputfiber coupling device 20 c are disposed offset from, but symmetricallyabout, the optical axis Z-Z of the multiplexing device 10 so as toinsure that the multiplexed, polychromatic optical output beam 26 c isdirected to the optical output fiber 22 c secured to the output fibercoupling device 20 c, and not to any of the other optical output fibers22, or anywhere else. This offset spacing of the input fiber couplingdevice 14 c and the output fiber coupling device 20 c is determinedbased upon the focusing power of the collimating/focusing lens 16, aswell as the characteristics of the diffraction grating 18 and thewavelengths of each of the monochromatic optical input beams 24 c.

Each of the plurality of monochromatic optical input beams 24 aretransmitted from their corresponding optical input fiber 12 into the airspace between the plurality of input fiber coupling devices 14 and thecollimating/focusing lens 16. Within this air space, the plurality ofmonochromatic optical input beams 24 are expanded in diameter until theybecome incident upon the collimating/focusing lens 16. Thecollimating/focusing lens 16 collimates each of the plurality ofmonochromatic optical input beams 24, and then transmits eachcollimated, monochromatic optical input beam 24′ to the reflectivediffraction grating 18.

At this point it should be noted that the optical axis of thecollimating/focusing lens 16 coincides with the optical axis Z-Z of themultiplexing device 10 so as to insure that the multiplexed,polychromatic optical output beam 26 a is directed to the optical outputfiber 22 a secured to the output fiber coupling device 20 a, and not toany of the other optical output fibers 22, or anywhere else, as will bedescribed in more detail below. Similarly, the optical axis of thecollimating/focusing lens 16 coincides with the optical axis Z-Z of themultiplexing device 10 so as to insure that the multiplexed,polychromatic optical output beam 26 b is directed to the optical outputfiber 22 b secured to the output fiber coupling device 20 b, and not toany of the other optical output fibers 22, or anywhere else, as will bedescribed in more detail below. Similarly still, the optical axis of thecollimating/focusing lens 16 coincides with the optical axis Z-Z of themultiplexing device 10 so as to insure that the multiplexed,polychromatic optical output beam 26 c is directed to the optical outputfiber 22 c secured to the output fiber coupling device 20 c, and not toany of the other optical output fibers 22, or anywhere else, as will bedescribed in more detail below.

The reflective diffraction grating 18 operates to angularly disperse theplurality of collimated, monochromatic optical input beams 24′ by anamount that is dependent upon the wavelength of each of the plurality ofcollimated, monochromatic optical input beams 24′. Also, the reflectivediffraction grating 18 is oriented at a special angle (i.e., the Littrowdiffraction angle, α_(i)) relative to the optical axis Z-Z of themultiplexing device 10 in order to obtain the Littrow diffractioncondition for an optical beam having a wavelength that lies within ornear the wavelength range of the plurality of collimated, monochromaticoptical input beams 24′. The Littrow diffraction condition requires thatan optical beam be incident on and reflected back from a reflectivediffraction grating at the exact same angle. Therefore, it will bereadily apparent to one skilled in the art that the reflectivediffraction grating 18 is used to obtain near-Littrow diffraction foreach of the plurality of collimated, monochromatic optical input beams24′.

The Littrow diffraction angle, α_(i), is determined by the well-knowndiffraction grating equation,

mλ=2d(sin α_(i))

wherein m is the diffraction order, λ is the wavelength, d is thediffraction grating groove spacing, and α_(i) is the common angle ofincidence and reflection. It will be readily apparent to one skilled inthe art that the Littrow diffraction angle, α_(i), depends upon numerousvariables, which may be varied as necessary to optimize the performanceof the multiplexing device 10. For example, variables affecting theLittrow diffraction angle, α_(i), include the desired gratingdiffraction order, the grating blaze angle, the number of data channels,the spacing of the data channels, and the wavelength range of themultiplexing device 10.

At this point it should be noted that the reflective diffraction grating18 can be formed from a variety of materials and by a variety oftechniques. For example, the reflective diffraction grating 18 can beformed by a three-dimensional hologram in a polymer medium, or byreplicating a mechanically ruled master with a polymer material. In bothcases, the polymer is overcoated with a thin, highly reflective metallayer such as, for example, gold or aluminum. Alternatively, thereflective diffraction grating 18 can be formed by chemically etchinginto a planar material such as, for example, glass or silicon, which isalso overcoated with a thin, highly reflective metal layer such as, forexample, gold or aluminum.

As previously mentioned, the reflective diffraction grating 18 operatesto angularly disperse the plurality of collimated, monochromatic opticalinput beams 24′. Thus, the reflective diffraction grating 18 removes theangular separation of the plurality of collimated, monochromatic opticalinput beams 24′a, and reflects a collimated, polychromatic opticaloutput beam 26′a back towards the collimating/focusing lens 16. Thecollimated, polychromatic optical output beam 26′a contains each of theunique wavelengths of the plurality of collimated, monochromatic opticalinput beams 24′a. Thus, the collimated, polychromatic optical outputbeam 26′a is a collimated, multiplexed, polychromatic optical outputbeam 26′a. The collimating/focusing lens 16 focuses the collimated,multiplexed, polychromatic optical output beam 26′a, and then transmitsthe resulting multiplexed, polychromatic optical output beam 26 a to theoutput fiber coupling device 20 a where it becomes incident upon theoptical output fiber 22 a. The multiplexed, polychromatic optical outputbeam 26 a is then coupled into the optical output fiber 22 a fortransmission therethrough.

Similarly, the reflective diffraction grating 18 removes the angularseparation of the plurality of collimated, monochromatic optical inputbeams 24′b, and reflects a collimated, polychromatic optical output beam26′b back towards the collimating/focusing lens 16. The collimated,polychromatic optical output beam 26′b contains each of the uniquewavelengths of the plurality of collimated, monochromatic optical inputbeams 24′b. Thus, the collimated, polychromatic optical output beam 26′bis a collimated, multiplexed, polychromatic optical output beam 26′b.The collimating/focusing lens 16 focuses the collimated, multiplexed,polychromatic optical output beam 26′b, and then transmits the resultingmultiplexed, polychromatic optical output beam 26 b to the output fibercoupling device 20 b where it becomes incident upon the optical outputfiber 22 b. The multiplexed, polychromatic optical output beam 26 b isthen coupled into the optical output fiber 22 ba for transmissiontherethrough.

Similarly still, the reflective diffraction grating 18 removes theangular separation of the plurality of collimated, monochromatic opticalinput beams 24′c, and reflects a collimated, polychromatic opticaloutput beam 26′c back towards the collimating/focusing lens 16. Thecollimated, polychromatic optical output beam 26′c contains each of theunique wavelengths of the plurality of collimated, monochromatic opticalinput beams 24′c. Thus, the collimated, polychromatic optical outputbeam 26′c is a collimated, multiplexed, polychromatic optical outputbeam 26′c. The collimating/focusing lens 16 focuses the collimated,multiplexed, polychromatic optical output beam 26′c, and then transmitsthe resulting multiplexed, polychromatic optical output beam 26 c to theoutput fiber coupling device 20 c where it becomes incident upon theoptical output fiber 22 c. The multiplexed, polychromatic optical outputbeam 26 c is then coupled into the optical output fiber 22 c fortransmission therethrough.

At this point it should be noted that the plurality of optical inputfibers 12 could be replaced in the multiplexing device 10 by acorresponding plurality of laser diodes 28 secured within a plurality ofcoupling devices 30, such as shown in FIG. 2a (although FIG. 2a showsonly a single 1×4 array). The coupling device 30 performs a similarfunction to that of each of the plurality of input fiber couplingdevices 14, that being to precisely group the plurality of laser diodes28 into a one-dimensional input array. The plurality of laser diodes 28are used in place of the plurality of optical input fibers 12 totransmit the plurality of monochromatic optical input beams 24 to themultiplexing device 10. The array of laser diodes 28, as well as theplurality of optical input fibers 12, may operate alone, or may be usedwith appropriate focusing lenses (not shown) to provide the bestcoupling and the lowest amount of signal loss and channel crosstalk.

At this point it should be noted that the multiplexing device 10, aswell as all of the multiplexing devices described herein, may beoperated in a converse configuration as a demultiplexing device 40, suchas shown in FIGS. 3a and 3 b. The demultiplexing device 40 is physicallyidentical to the multiplexing device 10, and is therefore numericallyidentified as such. However, the demultiplexing device 40 isfunctionally opposite to the multiplexing device 10. That is, aplurality of multiplexed, polychromatic optical input beams 42 aretransmitted from the plurality of optical fibers 22, and a plurality ofmonochromatic optical output beams 44 are transmitted to the pluralityof optical fibers 12, wherein each one of the plurality of monochromaticoptical output beams 44 is transmitted to a corresponding one of theplurality of optical fibers 12. For example, the multiplexed,polychromatic optical input beam 42 a is simultaneously carrying aplurality of channels of data, each at a unique wavelength which ispreferably, but not required to be, within the infrared (IR) region ofthe electromagnetic spectrum. The plurality of monochromatic opticaloutput beams 44 a are each carrying a single channel of data at acorresponding one of the unique wavelengths of the multiplexed,polychromatic optical input beam 42 a. The multiplexed, polychromaticoptical input beam 42 a is separated into the plurality of monochromaticoptical output beams 44 a through the combined operation of thecollimating/focusing lens 16 and the reflective diffraction grating 18.Thus, the collimating/focusing lens 16 and the reflective diffractiongrating 18 operate to perform a demultiplexing function.

Similarly, the multiplexed, polychromatic optical input beam 42 b issimultaneously carrying a plurality of channels of data, each at aunique wavelength which is preferably, but not required to be, withinthe infrared (IR) region of the electromagnetic spectrum. The pluralityof monochromatic optical output beams 44 b are each carrying a singlechannel of data at a corresponding one of the unique wavelengths of themultiplexed, polychromatic optical input beam 42 b. The multiplexed,polychromatic optical input beam 42 b is separated into the plurality ofmonochromatic optical output beams 44 b through the combined operationof the collimating/focusing lens 16 and the reflective diffractiongrating 18. Thus, the collimating/focusing lens 16 and the reflectivediffraction grating 18 operate to perform a demultiplexing function.

Similarly still, the multiplexed, polychromatic optical input beam 42 cis simultaneously carrying a plurality of channels of data, each at aunique wavelength which is preferably, but not required to be, withinthe infrared (IR) region of the electromagnetic spectrum. The pluralityof monochromatic optical output beams 44 c are each carrying a singlechannel of data at a corresponding one of the unique wavelengths of themultiplexed, polychromatic optical input beam 42 c. The multiplexed,polychromatic optical input beam 42 c is separated into the plurality ofmonochromatic optical output beams 44 c through the combined operationof the collimating/focusing lens 16 and the reflective diffractiongrating 18. Thus, the collimating/focusing lens 16 and the reflectivediffraction grating 18 operate to perform a demultiplexing function.

At this point it should be noted that the plurality of optical fibers 12could be replaced in the demultiplexing device 40 by a correspondingplurality of photodetectors 48 secured within a plurality of couplingdevices 50, such as shown in FIG. 2b (although FIG. 2b shows only asingle 1×13 array). The coupling device 50 performs a similar functionto that of each of the plurality of fiber coupling devices 14, thatbeing to precisely group the plurality of photodetectors 48 into aone-dimensional input array. The plurality of photodetectors 48 are usedin place of the plurality of optical fibers 12 to receive the pluralityof monochromatic optical output beams 44 from the demultiplexing device40. The array of photodetectors 48, as well as the plurality of opticalfibers 12, may operate alone, or may be used with appropriate focusinglenses (not shown) to provide the best coupling and the lowest amount ofsignal loss and channel crosstalk.

Referring to FIG. 4, there is shown a demultiplexing system 60 whereinthe demultiplexing device 40 of FIGS. 3a and 3 b is used in a practicalmanner to demultiplex additional data channels without requiringadditional WDM devices or significant design modifications in accordancewith the present invention. The demultiplexing system 60 is physicallyidentical to the multiplexing device 40, except for the addition ofoptical input fiber 62 and optical filter 64, and is thereforenumerically identified as such. The optical input fiber 62 communicatesa single, multiplexed, polychromatic optical input beam to the opticalfilter 64. The single, multiplexed, polychromatic optical input beambeing communicated by the optical input fiber 62 is simultaneouslycarrying a plurality of channels of data (e.g., 99 channels of data),each at a unique wavelength which is preferably, but not required to be,within the infrared (IR) region of the electromagnetic spectrum. Theoptical filter 64 equally splits the single, multiplexed, polychromaticoptical input beam according to wavelength into three multiplexed,polychromatic optical input beams 42. That is, each of the threeresulting multiplexed, polychromatic optical input beams 42 issimultaneously carrying a plurality of channels of data (e.g., 33channels of data) at the unique wavelengths of corresponding ones of theunique wavelengths of the single, multiplexed, polychromatic opticalinput beam. For example, the multiplexed, polychromatic optical inputbeam 42 a is simultaneously carrying a plurality of channels of data(e.g., 33 channels of data) at the unique wavelengths of correspondingones of the unique wavelengths of the single, multiplexed, polychromaticoptical input beam. Then, the plurality of monochromatic optical outputbeams 44 a are each carrying a single channel of data at a correspondingone of the unique wavelengths of the multiplexed, polychromatic opticalinput beam 42 a. The multiplexed, polychromatic optical input beam 42 ais separated into the plurality of monochromatic optical output beams 44a through the combined operation of the collimating/focusing lens 16 andthe reflective diffraction grating 18. Thus, the collimating/focusinglens 16 and the reflective diffraction grating 18 operate to perform ademultiplexing function.

Similarly, the multiplexed, polychromatic optical input beam 42 b issimultaneously carrying a plurality of channels of data (e.g., 33channels of data) at the unique wavelengths of corresponding ones of theunique wavelengths of the single, multiplexed, polychromatic opticalinput beam. Then, the plurality of monochromatic optical output beams 44b are each carrying a single channel of data at a corresponding one ofthe unique wavelengths of the multiplexed, polychromatic optical inputbeam 42 b. The multiplexed, polychromatic optical input beam 42 b isseparated into the plurality of monochromatic optical output beams 44 bthrough the combined operation of the collimating/focusing lens 16 andthe reflective diffraction grating 18. Thus, the collimating/focusinglens 16 and the reflective diffraction grating 18 operate to perform ademultiplexing function.

Similarly still, the multiplexed, polychromatic optical input beam 42 cis simultaneously carrying a plurality of channels of data (e.g., 33channels of data) at the unique wavelengths of corresponding ones of theunique wavelengths of the single, multiplexed, polychromatic opticalinput beam. Then, the plurality of monochromatic optical output beams 44c are each carrying a single channel of data at a corresponding one ofthe unique wavelengths of the multiplexed, polychromatic optical inputbeam 42 c. The multiplexed, polychromatic optical input beam 42 c isseparated into the plurality of monochromatic optical output beams 44 cthrough the combined operation of the collimating/focusing lens 16 andthe reflective diffraction grating 18. Thus, the collimating/focusinglens 16 and the reflective diffraction grating 18 operate to perform ademultiplexing function.

At this point it should be noted that there are many alternateembodiments and uses for the present invention ultra-dense wavelengthdivision multiplexing/demultiplexing device. For example, the single,multiplexed, polychromatic optical input beam could be split unequallyaccording to wavelength. Alternatively, the single, multiplexed,polychromatic optical input beam could be split either equally orunequally according to beam intensity. Alternatively still, the single,multiplexed, polychromatic optical input beam could be split such thatany or all of the resultant multiplexed, polychromatic optical inputbeams are identical so as to create redundant channels. Alternativelystill, the single, multiplexed, polychromatic optical input beam couldbe split such that certain data channels are routed separately so as toprovide security as to those data channels. Thus, the optical filter 64could be, for example, a standard coupler, a fiber Bragg grating, aninterference filter, a bandpass filter, a power splitter, or any othersuitable splitting means.

At this point it should also be noted that the present inventionultra-dense wavelength division multiplexing/demultiplexing device canbe used simultaneously for multiplexing and demultiplexing operations.For example, the plurality of optical fibers 12 a can be used totransmit a corresponding plurality of monochromatic optical input beams24 a and the optical fiber 22 a can be used to receive a multiplexed,polychromatic, optical output beam 26 a, while simultaneously theoptical fiber 22 b can be used to transmit a multiplexed, polychromatic,optical input beam 42 b and the plurality of optical fibers 12 b can beused to receive a corresponding plurality of monochromatic opticaloutput beams 44 b.

At this point it should further be noted that it is within the scope ofthe present invention to provide an ultra-dense wavelength divisionmultiplexing/demultiplexing device in accordance with the presentinvention using any or all of the concepts and/or features described inU.S. patent application Ser. No. 09/257,045 Client Reference No.D-97031-CNT), filed Feb. 25, 1999; U.S. patent application Ser. No.09/323,094 Client Reference No. D-99001), filed Jun. 1, 1999; U.S.patent application Ser. No. 09/342,142 Client Reference No. D-99002),filed Jun. 29, 1999; U.S. patent application Ser. No. 09/382,492 ClientReference No. D-99004), filed Aug. 25, 1999; U.S. patent applicationSer. No. 09/382,624 Client Reference No. D-99005), filed Aug. 25, 1999;U.S. patent application Ser. No. 09/363,041 Client Reference No.D-99014), filed Jul. 29, 1999; U.S. patent application Ser. No.09/363,042 Client Reference No. D-99015), filed Jul. 29, 1999; U.S.patent application Ser. No. 09/392,670 Client Reference No. D-99016),filed Sep. 8, 1999; and U.S. patent application Ser. No. 09/392,831Client Reference No. D-99017), filed Sep. 8, 1999; all of which arehereby incorporated herein by reference. For example, an ultra-densewavelength division multiplexing/demultiplexing device in accordancewith the present invention may be wholly or partially integrated, anddifferent types of lenses and lens configurations may be used.

Finally, it should be noted that the maximum number of arrays is onlydependent upon the ability of the lens design to handle more than onearray. Specifically, this relates to a basic tradeoff in performance asarrays are stacked next to one another. The farther away an array isplaced from the optical axis Z-Z of the device, typically there is adegradation in fiber coupling efficiency since the lens cannot typicallyperform at very large field heights with high efficiency. Also, asarrays are placed away from the optical axis Z-Z of the device, there isan increased probability of crosstalk. However, by careful lens design,the performance of each array can be made to be the same as otherarrays. For example, the inner-most array can be made to have the sameperformance as the outermost array. This could be useful for WDM systemsrequiring a very flat response between each of the data channels.Alternately, the placement of the arrays can be such that there is anon-flat, or unusual response (efficiency versus wavelength). The beautyof the present invention approach is that there is no significantinsertion loss for creating a WDM device with very high data channelcounts. This approach allows processing of more data channels in a moreefficient manner than other WDM technologies such as, for example, fiberBragg gratings or array waveguide gratings (AWGs). Also, the robustnessof this approach allows a very large number of data channels to beprocessed (multiplexed or demultiplexed) in one single WDM device. Thus,the present invention ultra-dense wavelength divisionmultiplexing/demultiplexing device has the benefits of low insertionloss, low crosstalk, low cost, and a very high number of data channels.More specifically, the present invention ultra-dense wavelength divisionmultiplexing/demultiplexing device offers the new and non-obviousadvantages of: (1) the ability to increase the data channel throughput(# of data channels) in a WDM device by simply splitting a signal andthen attaching corresponding split signal optical fibers to extra inputand output positions on the WDM device; (2) the ability to use a WDMdevice for the multiplexing or demultiplexing for more than one array ofdata channels without major changes to the lens design of the WDMdevice; (3) the ability to use a WDM device for bi-directional andsimultaneous multiplexing and demultiplexing (use as a duplexmux/demux); (4) the ability to create a redundant or secure WDM device;and (5) the other new and non-obvious advantages that are apparent fromthe foregoing description.

The present invention is not to be limited in scope by the specificembodiments described herein. Indeed, various modifications of thepresent invention, in addition to those described herein, will beapparent to those of skill in the art from the foregoing description andaccompanying drawings. Thus, such modifications are intended to fallwithin the scope of the appended claims.

What is claimed is:
 1. An ultra-dense wavelength division multiplexingdevice comprising: a wavelength division multiplexing device forcombining a first plurality of monochromatic optical beams into a firstsingle, multiplexed, polychromatic optical beam, and a second pluralityof monochromatic optical beams into a second single, multiplexed,polychromatic optical beam; a first plurality of optical input devicesdisposed proximate the wavelength division multiplexing device forcommunicating the first plurality of monochromatic optical beams to thewavelength division multiplexing device; a second plurality of opticalinput devices disposed proximate the wavelength division multiplexingdevice for communicating the second plurality of monochromatic opticalbeams to the wavelength division multiplexing device; a first opticaloutput device disposed proximate the wavelength division multiplexingdevice for receiving the first single, multiplexed, polychromaticoptical beam from the wavelength division multiplexing device; and asecond optical output device disposed proximate the wavelength divisionmultiplexing device for receiving the second single, multiplexed,polychromatic optical beam from the wavelength division multiplexingdevice.
 2. The device as defined in claim 1, wherein the wavelengthdivision multiplexing device comprises: a diffraction grating forcombining the first and second pluralities of monochromatic opticalbeams into the respective first and second single, multiplexed,polychromatic optical beams.
 3. The device as defined in claim 2,wherein the diffraction grating is a reflective diffraction gratingoriented at the Littrow diffraction angle.
 4. The device as defined inclaim 2, wherein the diffraction grating is a transmissive diffractiongrating.
 5. The device as defined in claim 1, wherein the wavelengthdivision multiplexing device comprises: a collimating lens forcollimating the first and second pluralities of monochromatic opticalbeams.
 6. The device as defined in claim 1, wherein the wavelengthdivision multiplexing device comprises: a boot lens for receiving thefirst and second pluralities of monochromatic optical beams from thefirst and second pluralities of optical input devices, respectively. 7.The device as defined in claim 1, wherein the wavelength divisionmultiplexing device comprises: a focusing lens for focusing the firstand second single, multiplexed, polychromatic optical beams.
 8. Thedevice as defined in claim 1, wherein the wavelength divisionmultiplexing device comprises: a boot lens for transmitting the firstand second single, multiplexed, polychromatic optical beams to the firstand second optical output devices, respectively.
 9. The device asdefined in claim 1, wherein the first plurality of optical input devicesis a first plurality of input optical fibers, each of the firstplurality of input optical fibers for communicating a respective one ofthe first plurality of monochromatic optical beams to the wavelengthdivision multiplexing device.
 10. The device as defined in claim 1,wherein the second plurality of optical input devices is a secondplurality of input optical fibers, each of the second plurality of inputoptical fibers for communicating a respective one of the secondplurality of monochromatic optical beams to the wavelength divisionmultiplexing device.
 11. The device as defined in claim 1, wherein thefirst plurality of optical input devices is a first plurality of laserdiode devices, each of the first plurality of laser diode devices forcommunicating a respective one of the first plurality of monochromaticoptical beams to the wavelength division multiplexing device.
 12. Thedevice as defined in claim 1, wherein the second plurality of opticalinput devices is a second plurality of laser diode devices, each of thesecond plurality of laser diode devices for communicating a respectiveone of the second plurality of monochromatic optical beams to thewavelength division multiplexing device.
 13. The device as defined inclaim 1, wherein the first optical output device is a first outputoptical fiber for receiving the first single, multiplexed, polychromaticoptical beam from the wavelength division multiplexing device.
 14. Thedevice as defined in claim 1, wherein the second optical output deviceis a second output optical fiber for receiving the second single,multiplexed, polychromatic optical beam from the wavelength divisionmultiplexing device.
 15. An ultra-dense wavelength divisiondemultiplexing device comprising: a wavelength division multiplexingdevice for separating a first single, multiplexed, polychromatic opticalbeam into a first plurality of monochromatic optical beams, and a secondsingle, multiplexed, polychromatic optical beam into a second pluralityof monochromatic optical beams; a first optical input device disposedproximate the wavelength division multiplexing device for communicatingthe first single, multiplexed, polychromatic optical beam to thewavelength division multiplexing device; a second optical input devicedisposed proximate the wavelength division multiplexing device forcommunicating the second single, multiplexed, polychromatic optical beamto the wavelength division multiplexing device; a first plurality ofoptical output devices disposed proximate the wavelength divisionmultiplexing device for receiving the first plurality of monochromaticoptical beams from the wavelength division multiplexing device; and asecond plurality of optical output devices disposed proximate thewavelength division multiplexing device for receiving the secondplurality of monochromatic optical beams from the wavelength divisionmultiplexing device.
 16. The device as defined in claim 15, wherein thewavelength division demultiplexing device comprises: a diffractiongrating for separating the first and second single, multiplexed,polychromatic optical beams into the respective first and secondpluralities of monochromatic optical beams.
 17. The device as defined inclaim 16, wherein the diffraction grating is a reflective diffractiongrating oriented at the Littrow diffraction angle.
 18. The device asdefined in claim 16, wherein the diffraction grating is a transmissivediffraction grating.
 19. The device as defined in claim 15, furthercomprising: a splitter for splitting a third single, multiplexed,polychromatic optical beam into at least the first and second single,multiplexed, polychromatic optical beams.
 20. The device as defined inclaim 19, wherein the third single, multiplexed, polychromatic opticalbeam is split according to one of: equally, unequally, beam wavelength,and beam intensity.
 21. The device as defined in claim 15, wherein thewavelength division demultiplexing device comprises: a focusing lens forfocusing the first and second pluralities of monochromatic opticalbeams.
 22. The device as defined in claim 15, wherein the wavelengthdivision demultiplexing device comprises: a boot lens for transmittingthe first and second pluralities of monochromatic optical beams to thefirst and second optical output devices, respectively.
 23. The device asdefined in claim 15, wherein the first optical input device is a firstinput optical fiber for communicating the first single, multiplexed,polychromatic optical beam to the wavelength division demultiplexingdevice.
 24. The device as defined in claim 15, wherein the secondoptical input device is a second input optical fiber for communicatingthe second single, multiplexed, polychromatic optical beam to thewavelength division demultiplexing device.
 25. The device as defined inclaim 15, wherein the first plurality of optical output devices is afirst plurality of output optical fibers, each of the first plurality ofoutput optical fibers for receiving a respective one of the firstplurality of monochromatic optical beams from the wavelength divisiondemultiplexing device.
 26. The device as defined in claim 15, whereinthe second plurality of optical output devices is a second plurality ofoutput optical fibers, each of the second plurality of output opticalfibers for receiving a respective one of the second plurality ofmonochromatic optical beams from the wavelength division demultiplexingdevice.
 27. The device as defined in claim 15, wherein the firstplurality of optical output devices is a first plurality ofphotodetectors, each of the first plurality of photodetectors forreceiving a respective one of the first plurality of monochromaticoptical beams from the wavelength division demultiplexing device. 28.The device as defined in claim 15, wherein the second plurality ofoptical output devices is a second plurality of photodetectors, each ofthe second plurality of photodetectors for receiving a respective one ofthe second plurality of monochromatic optical beams from the wavelengthdivision demultiplexing device.
 29. The device as defined in claim 15,wherein the wavelength division demultiplexing device comprises: a bootlens for receiving the first and second single, multiplexed,polychromatic optical beams from the first and second optical inputdevices, respectively.
 30. The device as defined in claim 15, whereinthe wavelength division demultiplexing device comprises: a collimatinglens for collimating the first and second single, multiplexed,polychromatic optical beams.
 31. An ultra-dense wavelength divisionmultiplexing/demultiplexing device comprising: a wavelength divisionmultiplexing/demultiplexing device for combining a first plurality ofmonochromatic optical beams into a first single, multiplexed,polychromatic optical beam, and for separating a second single,multiplexed, polychromatic optical beam into a second plurality ofmonochromatic optical beams; a first plurality of optical input devicesdisposed proximate the wavelength division multiplexing/demultiplexingdevice for communicating the first plurality of monochromatic opticalbeams to the wavelength division multiplexing/demultiplexing device; asecond optical input device disposed proximate the wavelength divisionmultiplexing/demultiplexing device for communicating the second single,multiplexed, polychromatic optical beam to the wavelength divisionmultiplexing/demultiplexing device; a first optical output devicedisposed proximate the wavelength division multiplexing/demultiplexingdevice for receiving the first single, multiplexed, polychromaticoptical beam from the wavelength division multiplexing/demultiplexingdevice; and a second plurality of optical output devices disposedproximate the wavelength division multiplexing/demultiplexing device forreceiving the second plurality of monochromatic optical beams from thewavelength division multiplexing/demultiplexing device.
 32. A method forincreasing channel throughput in a wavelength division demultiplexingdevice, the method comprising the steps of: splitting a single,multiplexed, polychromatic optical beam into at least two multiplexed,polychromatic optical beams; and separating each of the at least twomultiplexed, polychromatic optical beams into a respective at least twopluralities of monochromatic optical beams.
 33. The method as defined inclaim 31, further comprising the step of: collimating each of the atleast two multiplexed, polychromatic optical beams.
 34. The method asdefined in claim 31, further comprising the step of: focusing therespective at least two pluralities of monochromatic optical beams.